1. Field of the Invention
The present invention relates generally to systems and methods for providing oxygen therapy and, more particularly, to systems and methods for providing variable flow oxygen therapy.
2. Description of the Related Art
A growing number of people in the United States suffer from chronic obstructive pulmonary disease (COPD) such as asthma and emphysema, as well as cystic fibrosis, lung cancer, lung injuries, cardiovascular diseases, and otherwise diseased or damaged lungs. Although there is no cure for many of these conditions, their detrimental impact of can be mitigated by the prescription of oxygen therapy. The inhalation of oxygen-enriched gas serves to compensate for the poor function of the patient's lungs in absorbing oxygen.
More and more people are using oxygen therapy outside the hospital, permitting them to lead active, productive lives. Recent developments in oxygen therapy technology have given those dependent upon oxygen a variety of in-home and portable options for oxygen therapy. There are three main ways to personally administer oxygen therapy outside of a medical facility, (1) oxygen concentrators, (2) liquid oxygen devices, and (3) compressed gas devices. Each of these three types of solutions provide particular benefits and detriments.
First, oxygen concentrators or pressure swing adsorption systems are an excellent source of oxygen therapy for in home use. Pressure swing adsorption (“PSA”) systems are advantageous in that they can process ambient air, containing approximately 21% oxygen, and separate that oxygen from the ambient air. Thereby the user can be supplied with higher concentrations of oxygen. While suitable for their intended purpose, oxygen concentrators are generally bulky and require access to a power source, such as an electrical outlet. Thus, oxygen concentrators are ill-suited for portability and are not intended for use with an ambulatory individual.
Second, liquid oxygen system (“LOX” system) can provide a convenient method of portable oxygen therapy. Liquid oxygen is advantageous because it occupies significantly less space of compressed gaseous oxygen. A conventional LOX system includes a large stationary LOX storage canister that stays in the home. The conventional system also includes a small, portable delivery apparatus that can be filled from the stationary unit for trips outside the home. Many first generation systems have limited utilization due to the low LOX capacity of the portable delivery apparatus and the administered LOX flow rate. To maintain a liquid state, oxygen must be kept at a relatively cool temperature around 300 degrees Fahrenheit below zero. Therefore, the liquid oxygen stored in LOX systems will evaporate even if not used by the user. In this manner, the LOX system has a relatively short use period that expires regardless of whether the user is actually using the oxygen.
Third, compressed oxygen systems are generally prescribed when oxygen is not needed all the time, such as only when walking or performing physical activity. Small compressed oxygen tanks are well suited for portability in that they can be relatively light weight and they can maintain their supply of oxygen when not in use. Small portable compressed oxygen devices are limited, however, in how long they will last depending on the prescribed flow rate and type of tank. Therefore, portable compressed oxygen devices must be refilled often.
While suitable for their intended purposes, conventional oxygen delivery devices suffer from many drawbacks. For example, many conventional oxygen delivery devices are unable to provide oxygen delivery at different flow rates. Furthermore, existing oxygen delivery devices cannot provide phasic oxygen delivery at various flow rates. Moreover, conventional pulse mode devices can irritate the patient, especially when the patient is attempting to go to sleep. Additionally, many conventional devices are unable to provide a reliable and sustained method of backup oxygen delivery.